Strip Search

Strip-till outstripped both no-till and conventional tillage in a two-year comparison of corn tillage methods by the University of Minnesota.

On-farm trials found that fall strip-tillage protected soil from erosion and moisture loss without sacrificing yield. And it produced higher net returns than either no-till or chisel plowing.

“Strip-tillage creates a warm, dry seedbed that makes it possible to match the early planting dates and high yields of conventional tillage, while its heavy residue cover provides the erosion control and improved water infiltration that no-till offers,” says Jodi DeJong-Hughes, a University of Minnesota (U of M) Extension crops specialist who led the on-farm trials.

In the northern Corn Belt, no-till corn production is a real challenge most years, DeJong-Hughes says. Cool, wet springs combined with a blanket of residue often delay planting. Cold soils retard germination and early growth, resulting in uneven stands.

Fall strip tillage has evolved as a way to overcome these conditions. Crop residue is cleared from a strip about 10 in. wide. In the same operation, fertilizer is banded 5-8 in. deep beneath the tilled zone. Coulters and sweeps on the fertilizer toolbar build a mound of bare, loosened soil about 4 in. high, where the seed will be planted the following spring. The tilled soil drains and warms up faster, allowing earlier planting. Row middles are left undisturbed, preserving the residue cover between the strips.

The Minnesota research compared strip tillage with three other common tillage systems for corn following soybeans:

Fall chisel plow plus spring cultivation;

Shallow spring cultivation; and

No-till.

The side-by-side trials were conducted in 2004 and 2005 at 10 farms in southern Minnesota.

In 2004, unusually cool, wet weather — plus frost on August 21 — made for disappointing corn yields in general, and a “worst-case scenario” for no-till corn, DeJong-Hughes says. At six out of 10 farms, no-till yields suffered significantly, compared to the other tillage treatments. By contrast, strip-till yields held up just fine. In 2005, conditions for crop growth in southern Minnesota were ideal, and corn yields were exceptional all around. Strip-till and chisel-plow corn showed small yield advantages, but differences were not significant in most cases.

The on-farm tillage trials confirm the findings from a decade of small plot research by the University of Minnesota, says U of M soil scientist Jeff Vetch. In 31 site-years of tillage research, there has been no significant difference in average corn yields with chisel plow plus spring cultivation, one-pass spring cultivation or strip tillage, he says. No-till corn yields averaged 5-7% lower than the other three tillage systems.

Some no-till farmers are looking at strip-tillage because they've got compaction problems. Others may qualify for conservation incentives if they switch to reduced tillage systems. Improved machinery and advances in corn genetics, such as stronger stalks, are also pushing interest in strip tillage.

Jeff Olson started experimenting with fall strip-tillage in 2001. He raises corn, soybeans, navy beans and winter wheat on heavy, level ground in western Minnesota.

“Our biggest challenge in the spring is cold soils,” Olson says. He has adopted no-till for soybeans and winter wheat, “but I've found that no-till for corn is pretty challenging in our area.” With strip tillage, “you've got a warmer seedbed, and there's no traffic over it,” says Olson, who used it for 300 acres of corn in 2006. “The soil in the strips is very mellow and garden-like.”

Research at Iowa State University found that tilled strips are 2-3 warmer than the surrounding residue-covered soil, says Mahdi Al-Kaisi, an Iowa Extension soil scientist. But that's only in wet soils, he adds. “In well-drained soils, the temperature difference isn't there. Strip-till has an advantage in areas where farmers have poorly drained soil and wet conditions.”

In spring, strips are usually easy to see, “so you can pick your dry areas, or even start planting in the middle of a field,” Olson says. And running equipment over the old residue “goes pretty well.”

Olson says his corn yields in a strip-tillage system have been comparable to a chisel system. “We're not giving up or gaining anything in yield.” And his residue counts have come way up, reaching “50-52% this year. For soybean stubble, that's really good.”

Strip-tillage has cut Olson's corn input costs, too. With fewer trips across the field, “fuel and labor are less,” he says. “And I'm banding less fertilizer than I was broadcasting.” In the fall, he blows down phosphorus and potassium, and injects 100 lbs./acre of anhydrous, 7 in. deep. In the spring, he bands 7 gal./acre of starter fertilizer as an insurance policy.

In strip-tillage, as in other conservation-tillage systems, nitrogen fertilizer should be placed below the soil surface for most efficient use, says George Rehm, U of M soil scientist. He also advises split applications of nitrogen. In addition, “there's general agreement that banded applications of phosphate and potash are necessary if a conservation tillage production system is to be successful,” he says.

The Minnesota study also compared tillage system costs and revenues. In evaluating economics, farmers should look at all the variables, says Minnesota Extension economist David Bau, who co-authored the tillage report. “Consideration must be given to the initial and maintenance costs of equipment, the size of tractor needed to pull the tool, equipment depreciation, labor costs, conservation program incentives and increased management costs related to fertilizer and pest management,” he says.

In the Minnesota study, field operations in a strip-till system averaged $57/acre for corn — $3/acre less than for conventional tillage. Savings came mainly from lower fuel costs, a finding that was confirmed by an April 2006 report from the University of Illinois. That study found that strip-till corn operations consumed 2.9 gal. of fuel per acre, on average, compared to 3.4 gal. for a conventional system.

Strip-till costs averaged $8/acre more than no-till in the Minnesota study. But the extra tillage expense was offset by an additional $14 of revenue per acre. When it came to net farm income, strip tillage surpassed conventional tillage by an average of $2.37/acre, and no-till by $5.50/acre, Bau reports.

Those results agree with Tom Muller's experience. Muller, who farms in southern Minnesota, has been strip-tilling corn since 1994, when he built his own tillage tool. Muller compared tillage side-by-side with the U of M for four years. It wasn't until the fourth year that yields from the strip-tilled corn topped the chisel-plowed corn, “but I still made more money on the strip-till corn every year. That's what keeps me in it. I'm making more money.”

Federal and state conservation incentives can help farmers acquire alternative tillage machinery. Jeff Olson is enrolled in NRCS's Environmental Quality Incentives Program (EQIP), an equipment cost-sharing plan that is paying him $30/acre for four years to convert 250 acres to strip-till.

A variety of tools can be used for strip-tilling, including anhydrous ammonia injection knives, row cleaners, double-disks and fluted coulters. Olson invested in a 12-row, 30-in. strip-till tool bar with a 5-ton dry fertilizer box. A C-shank cuts through the residue, and a mole knife loosens the soil and bands fertilizer. A pair of covering disks builds a 4-in.-high berm that settles by spring. “I was looking for something simple,” Olson says. “I've never plugged this.”

Olson likes the simplicity and cost savings of strip till. Still, he adds, there are some challenges. Without the first pass of the cultivator, winter annuals are more of a problem, so he's had to change his weed control program.

Because you're preparing the seedbed in the fall, you need a skillful operator to build the strips precisely and accurately, Olson says. “If you're not planting right over the center of the berm, the corn is definitely affected.” This year, Olson invested in guided steering technology. “That should help a lot,” he says.

But the biggest challenge with fall strip-tillage is the labor crunch. “There's so much to do already in the fall,” says Olson, who raises hogs and seeds winter wheat after his soybeans come off. Banding fall anhydrous means delaying tillage until soil temperatures drop to 50, which squeezes the number of days he has to get it done.

Fall strip-tillage certainly isn't the answer for everyone, says DeJong-Hughes, the Minnesota Extension specialist. If your soils are medium- to light-textured, no-till or shallow spring cultivation may be the best choice, she says. But in the right circumstances, strip-tillage can be practiced with “minimal effect on crop yields and often at lower production costs than conventional tillage.”